Command line Elliptic Curve operations - JohnHau/mis GitHub Wiki

OpenSSL® provides the following command-line tools to work with keys suitable for Elliptic Curve (EC) Cryptography algorithms:

openssl ecparam openssl ec Currently, OpenSSL supports the following EC algorithms:

Elliptic Curve Diffie Hellman (ECDH) for key agreement Elliptic Curve Digital Signature Algorithm (ECDSA) for signing and verifying ecparams and ec do not support the x25519, ed25519, and ed448 curves. See the genpkey subcommand for information about those curves.

EC private key file formats OpenSSL uses Privacy Enhanced Mail (PEM) files to store EC private keys by default. These files contain base-64 encoded data and use the .pem extension. The following example shows a private key file in PEM format.

-----BEGIN EC PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: DES-EDE3-CBC,258248872DB25390

JIzhns0nRb+pj6RONAijJli8Rhu2bIrw8D+ruHEWL1IEH6Q5tvzqAI2PDYXbSzCn 24JPWx9khmTu6ijerANNYYk0p2Pjxr12MAYpqgtXbRrXLF4AIomzYWq16BH7Y63o zvqWMBJO6tQ5RHPLM2FmweyPB/XSL7KvLTe+g6pz/W9wf52CyQ/VeK+yBXqEi7QF 0f9EKRlePRLAUcQPD4nkckcywX6Nz+TW/SOKt38YytM9MyQsAfcxu7u0nl/dLylk n57qUm3nk0z0moYJbfLx59eP0/go8VjeP2fRKkgz1DOM7VkmtPrC7vnyRpKsnP2S 6n6uacerkNXTmUcz7mTCGGfrsBeACJeX1gwinDZVwkzDxNKhLXOlFFAMWE+SeiFp kDny2v3D8sU= -----END EC PRIVATE KEY----- The following example shows a private key file that uses the Public Key Cryptography Standard 8 (PKCS8) in PEM format.

Use the following command to convert a PKCS8 file to a traditional encrypted EC key file:

openssl ec -aes-128-cbc -in p8file.pem -out tradfile.pem

Replace argument -aes-128-cbc with any other valid OpenSSL cipher name. (See the OpenSSL documentation for a list of valid cipher names.)

Use the following command to convert a PKCS8 file to a traditional unencrypted EC key file:

openssl ec -in p8file.pem -out tradfile.pem

Use the following command to convert an EC key file to encrypted PKCS8 format:

openssl pkcs8 -topk8 -in tradfile.pem -out p8file.pem

Use the following command to convert an EC key file to unencrypted PKCS8 format:

openssl pkcs8 -topk8 -nocrypt -in tradfile.pem -out p8file.pem

Note: The EC private key files are not encrypted by default. You must explicitly set the file to encrypted and specify the cipher algorithm. The PKCS8 files are encrypted by default. Use the -nocrypt option to set the file to unencrypted.

A PEM file is DER data encoded by using base 64 encoding rules, with a header and footer. PEM files are human-readable, so they are more convenient to use. However, you can store all the files shown above in DER format. DER format is a binary format, and unlike a PEM file, it is not human-readable.

Most openssl commands have options -inform DER and -outform DER. -inform DER specifies that the input file is DER, and -outform DER specifies that the output file is DER.

Use the following command to convert the PKCS8 format to a traditional encrypted EC key in DER format.

openssl ec -in p8file.pem -outform DER -out tradfile.der

You cannot encrypt a traditional EC private key file in DER format. If you attempt to do so, the command silently ignores the argument. However, you can encrypt PKS8 files in DER format.

Use the following command to convert a traditional EC key file to encrypted PKCS8 in DER format:

openssl pkcs8 -topk8 -in tradfile.pem -outform DER -out p8file.der

EC public key file formats PEM format supports several types of public keys in OpenSSL. The following file shows EC public keys in PEM format.

openssl ec -in ecprivkey.pem -pubout -out ecpubkey.pem

Use the following command to create a public key file from a private key file in DER format:

openssl ec -in ecprivkey.pem -pubout -outform DER -out ecpubkey.der

Generating EC keys and parameters The EC parameters file contains all the information necessary to define an elliptic curve for cryptographic operations. OpenSSL uses ECDH and ECDSA algorithms. Use the following command to obtain a list of built-in curves:

openssl ecparam -list_curves

Use the following command to generate an EC parameters file of curve secp256k1:

openssl ecparam -name secp256k1 -out secp256k1.pem

Replace secp256k1 with any other name obtained from the openssl ecparam -list_curves command.

You can generate keys by using the ecparam command, either by using a pre-existing parameters file or by using the name of the curve. Use the following command to generate a private/public key pair from a parameters file:

openssl ecparam -in secp256k1.pem -genkey -noout -out secp256k1-key.pem

Use the following command to generate a private/public key pair from the name of the curve:

openssl ecparam -name secp256k1 -genkey -noout -out secp256k1-key.pem

The key file has the information of the parameters used to generate the key embedded. OpenSSL stores the name of the curve in the parameters file or the key file. It does not explicitly store the full set of parameters associated with the name by default. Use the following command to confirm the name of the curve in the parameters file:

openssl ecparam -in secp256k1.pem -text -noout

Example output:

ASN1 OID: secp256k1

Use the following command to list parameter details from a parameters file:

openssl ecparam -in secp256k1.pem -text -param_enc explicit -noout

Use the following command to list parameter details from the name of a curve, substituting the name of the curve accordingly:

openssl ecparam -name secp256k1 -text -param_enc explicit -noout

Example output:

Field Type: prime-field Prime: 00:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff: ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:fe:ff: ff:fc:2f A: 0 B: 7 (0x7) Generator (uncompressed): 04:79:be:66:7e:f9:dc:bb:ac:55:a0:62:95:ce:87: 0b:07:02:9b:fc:db:2d:ce:28:d9:59:f2:81:5b:16: f8:17:98:48:3a:da:77:26:a3:c4:65:5d:a4:fb:fc: 0e:11:08:a8:fd:17:b4:48:a6:85:54:19:9c:47:d0: 8f:fb:10:d4:b8 Order: 00:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff:ff: ff:fe:ba:ae:dc:e6:af:48:a0:3b:bf:d2:5e:8c:d0: 36:41:41 Cofactor: 1 (0x1) You can generate parameter files and key files that explicitly include the full set of parameters instead of just the name of the curve. This is important when some target systems don’t know the details of the curve. OpenSSL version 1.0.2 added new curves, such as brainpool512t1. Earlier versions of OpenSSL that use a parameter file or key file configured with brainpool512t1 result in the following error:

bash$ openssl ecparam -in brainpoolP512t1.pem -text -noout unable to load elliptic curve parameters 140138321110720:error:1009E077:elliptic curve routines:EC_ASN1_PKPARAMETERS2GROUP:ec group new by name failure:ec_asn1.c:1035: 140138321110720:error:1009107F:elliptic curve routines:d2i_ECPKParameters:pkparameters2group failure:ec_asn1.c:1080: 140138321110720:error:0906700D:PEM routines:PEM_ASN1_read_bio:ASN1 lib:pem_oth.c:83: Use explicit parameters to avoid this problem, as shown in the following command with OpenSSL 1.0.2:

openssl ecparam -name brainpoolP512t1 -out brainpoolP512t1.pem -param_enc explicit

The command yields a longer parameters file with all the parameters.

openssl ecparam -in brainpoolP512t1.pem -text -noout

OpenSSL version 1.0.1. displays the parameters even if it doesn’t know the curve.

Use the following command to generate a key file with explicit parameters:

openssl ecparam -name brainpoolP512t1 -genkey -noout -out brainpoolP512t1-key.pem -param_enc explicit

Earlier versions of OpenSSL can process the key file you obtain.

Note: After the parameters change to explicit parameters, don’t revert the changes. There is no utility to find which explicit parameters correspond to a curve.

Command line Elliptic Curve operations - JohnHau/mis GitHub Wiki

⚠️ **GitHub.com Fallback** ⚠️

⚠️ GitHub.com Fallback ⚠️